Young people growing up in some of England's most deprived areas are being held back from a career in medicine as they are less likely to have the opportunity to study separate sciences at GCSE, a doctors' union has warned.
The British Medical Association (BMA) said it was concerning that 80% of all medical students in the UK come from just 20% of the country's schools.
It is calling for all secondary schools to offer triple science - separate GCSEs in biology, chemistry and physics - to students that request it, as it said it is the academic option favoured by the majority of medical schools.
Most pupils take double science, which is worth just two GCSEs.
The BMA said its analysis has found that fewer schools in deprived areas offer the three subjects separately, and at those that do, lower numbers of pupils study the qualification.
For instance, in Knowsley, Merseyside - an area with a high level of deprivation, it found only just over half (57.1%) the schools offer triple science, and only one in 10 students (11.4%) study it.
In contrast, it found that in Rutland, a more affluent area, all schools offer the separate subjects and more than a third of pupils (36.2%) have taken them up.
It also highlighted a particularly low number of students studying triple science in areas of deprivation in the North East and North West.
The union said it wants medical schools to use contextualised admissions, where universities consider additional information including further details about the applicant's school, and the area they grew up in.
It also suggests that medical schools work with local secondary schools to identify student potential and provide access courses and outreach schemes for these students.
Charlie Bell, the BMA's Medical Students Committee co-chair, said: "The chance of becoming a doctor should not be limited because of the failure of some schools to offer the qualifications that pupils need to apply for medical school - and the failure of universities to alter grade requirements accordingly.
"All secondary schools should facilitate the triple science GCSE for those who request it. Medical schools must also play a part in widening access by using contextualised admissions, which take a student's background into account, and by working with secondary schools to identify talent and support those who wish to pursue a career in medicine.
"At a time when the Government's decision to scrap educational maintenance grants will create further barriers to low-income students becoming doctors, it is vital that young people who wish to pursue medicine must be encouraged and supported, whatever their background."
Philip Smith, a gastroenterologist from London, was educated at an under-resourced comprehensive in Rochdale.
He said: "My school never had anybody interested in doing medicine - it was all very much a voyage of discovery for me and my mum and dad. At times it was a battle to keep focus.
"At medical school I went in to the first laboratory I'd ever been to for a practical exam and I'd never seen anything like it. For my A-level chemistry exams, our school had to borrow pipettes from a local grammar school.
"As a doctor you have to be able to relate to people from all spectrums of life. If you just take doctors from one tier of society, they won't have a concept of what life is like for people who aren't from a privileged background."